46 THE SOIL AND THE SAP 



Minute round-worms are creeping and wriggling through 

 the soil. Some of these spend their whole life there, others 

 only their larval existence, w^hilst others return to the soil 

 only when mature. A typical example of this is the round- 

 worm which causes disease in adult grouse. It leaves the 

 alimentary canal of the bird with the droppings and produces 

 its young on the soil. The larvae make their way to the 

 heather, and slowly wriggle up to the heather-buds which 

 form the favourite food of the mature grouse. With this food 

 they pass into the alimentary canal of the game bird, become 

 adult, and set up fresh trouble in the bird's intestine. It is 

 difficult for the layman to grasp what is going on in and on the 

 soil and on the plants which it supports. Suppose we could 

 by means of a gigantic lens magnify a square yard of a grouse 

 moor one hundred times. The heather plants would be as 

 tall as lofty elms, their flowers as big as cabbages, the grouse 

 would be about six or seven times the size of Rostand's 

 "Chantecler" at the Porte St Martin Theatre. Creeping and 

 wriggling up the stem and over the leaves and gradually yet 

 surely making their way towards the flowers would be seen 

 hundreds and thousands of silvery-white worms about the 

 size of young earthworms. Lying on the leaves and on the 

 plant generally would be seen thousands of spherical bodies 

 the size of grains of wheat, the cysts of the Coccidium — a 

 protozoan parasite which destroys the young grouse chick — 

 and on the ground and on the plants, as large as peas, would be 

 seen the grouse tape-worm eggs patiently awaiting the advent 

 of their second host. It is perhaps a picture which will not 

 appeal to all, but yet it represents what, unseen and un- 

 suspected, is always taking place on a grouse moor. 



Then there are innumerable insects, chiefly in the caterpillar 

 stage, which crawl through soft earth and do infinite harm to 

 trees, plants and crops by living on or nibbling their roots. 

 One of them, the Cicada, spends seventeen years as a larval 

 form in the earth in the southern part of the United States. 

 Many millipedes also live crawling in the soil. One of them, 

 known as the wire-worm^, does considerable damage. Again 



1 Another injurious animal, also unfortunately called a "wire- worm" 

 is the larva of a beetle, Elaler linealus. 



